This invention relates generally to image light projectors using high power light sources, such as high power arc lamps and more particularly to a cooling arrangement for high power arc lamp reflectors.
Image light projectors, especially those used for projecting a still or moving image onto or through a large screen, typically use high power arc lamps, that operate at 5000 to 7000 watts and higher. Such projectors are usually equipped with reflectors that generally surround the light sources in order to concentrate the desired components of the beam of light and render the image large enough and bright enough to be viewed by large numbers of viewers, for example. Because of the high power necessary to accomplish this projection task, the surface temperature of these high power lamp reflectors can reach levels that would damage the reflective coatings on the inside surface of the reflectors if adequate cooling of the reflector were not provided. Currently, in these large projectors, such cooling is typically accomplished by cooling apparatuses that convey water or other liquid coolant along the exterior surface of the reflector, between such exterior surface and a spaced-apart surrounding shroud.
Such liquid cooling systems thus require an external heat sink, generally in the form of an external heat exchanger, to cool the water or other liquid coolant, which is then recirculated back over the exterior surface of the reflector. This results in increased complexity and cost of such projector systems, both in terms of their initial purchase prices and the costs of maintenance of the projection equipment. Furthermore, these systems present the potential danger associated with water or other liquid coolant leaks in and around the various electrical components of the projector.
Previously, such liquid cooling systems have been necessary since air cooling systems had not proven to be adequate for such high power lamp devices unless other cooling systems, cooling apparatuses or features are used in conjunction with the air cooling scheme.
According to the present invention, however, a single air cooling system is provided that overcomes these disadvantages and provides adequate cooling for such high power lamp applications at a reasonable cost without the necessity of complex, high-maintenance external equipment. In a high power lamp device equipped with a cooling arrangement according to the present invention, a reflector generally surrounds the high-temperature light source with a shroud generally surrounding at least a portion of the reflector and spaced apart from its external surface. Typically, reflectors and shrouds of this type are of a generally bell-shaped configuration, having an apex end, at which the light source is located, and an open mouth end, with at least the reflector being defined by a curved surface of revolution circumferentially about a central axis passing through the apex. Such curved surface of revolution for the reflector can be generally elliptical, generally circular, or have yet other shapes adapted to meet the projection and light transmission requirements of the device.
A plurality of cooling fins are disposed along the exterior surface of the reflector and protrude generally radially outwardly therefrom in a direction toward the interior of the shroud. Such cooling fins are arranged in a plurality of spaced-part rows, with the rows extending along at least a portion of the exterior surface of the reflector from a location generally adjacent the apex of the reflector toward the mouth of the reflector. The cooling fins are spaced apart from one another within each of the rows, and the spaced-apart cooling fins in each row are offset in the axial direction relative to the spaced-apart cooling fins in at least one circumferentially-adjacent row of cooling fins.
Preferably, the circumferential distance between adjacent rows of cooling fins increases in a direction from the apex of the reflector toward the mouth of the reflector, with the cooling fins thus also preferably being offset in the circumferential direction with respect to their axially adjacent cooling fins in each row of cooling fins.
In order to provide this configuration of cooling fins and rows, the cooling fins are preferably arranged in pairs of circumferentially adjacent rows with the adjacent pairs being interconnected by a base plate. The base plate is affixed to the exterior surface of the reflector and curves outwardly from a location generally adjacent the apex of the reflector toward the mouth of the reflector, thus conforming closely to the exterior surface shape of the reflector. In a preferred form of the invention shown for purposes of illustration herein the cooling fins are all of the same radially outwardly protruding length. However, it should be noted that the present invention also encompasses cooling fins of varying lengths around the circumference of the reflector or along its axial length, if deemed necessary or suitable in a given application.
One of the advantages of the present invention, in addition to those mentioned above, is that the cooling effectiveness of the cooling systems of the present invention allows for the use of a wider variety of reflective surface coatings on the inside of the reflector, thus making the projection device more efficient and effective in projecting beams of light having the desired characteristics for a given application.
Additional objects, advantages, and features of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.